A rocky world about the size of Earth that could hold liquid water has been found orbiting around the star closest to our solar system, researchers announced Wednesday.

The planet orbits the star Proxima Centauri once every 11 days, and researchers with the European Southern Observatory said it's inside the habitable zone -- the area around a star in which liquid water could exist.

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At just over four light-years away, the planet, called Proxima b, is the closest exoplanet to Earth, and its mass and distance from its star mean it's also the nearest place that could possibly support life outside our solar system.

The researchers said they don't know if there is any water, and it might be impossible to tell. In order to determine the composition of an exoplanet's atmosphere, it typically must pass in front of its star, as observed from Earth. Scientists said they don't yet know if such an observation is possible.

"Many exoplanets have been found, and many more will be found, but searching for the closest potential Earth-analogue and succeeding has been the experience of a lifetime for all of us," said Guillem Anglada-Escude, the lead astronomer for the Pale Red Dot campaign, which made the discovery. "Many people’s stories and efforts have converged on this discovery. The result is also a tribute to all of them. The search for life on Proxima b comes next."

If there is life on Proxima b, it would have to be hardy. Proxima Centauri is a red dwarf star, so the planet is much closer to it than the Earth is to the sun. Because the star is cooler than the sun, that means the habitable zone is also closer to the star.

Researchers said the surface of the planet could be subject to intense ultraviolet and X-ray flares from the star, far more intense than what the Earth experiences.

Proxima b could also be tidally locked to the star, which means the same side faces it throughout its orbit. Half of the planet would be constant daylight, while the other side would experience constant night. Life as we know it might be most comfortable along the edge of the day-night boundary, where conditions could be less extreme.

But the possibility of life on Proxima b is nothing more than speculation. The researchers said they are continuing their observations to learn as much as possible about the newly discovered system.

And it might be possible to take a closer look. The StarShot project is a proposal to send a mission to Alpha Centauri, the triple star system that contains Proxima Centauri. The proposal would use lightsail technology to accelerate a small spacecraft to a fraction of light speed, theoretically enabling it to reach Alpha Centauri in a little more than 20 years.